This invention relates to an improved, stable, fluid suspension fertilizer composition and to a method for producing same. In one aspect the invention relates to an improved, stable, aqueous suspension fertilizer composition wherein monoammonium phosphate is employed as the source of phosphate and the monoammonium phosphate is reacted with ammonia in an amount effective to produce mole ratios of ammonia to phosphoric acid equivalent in the range of about 1.2:1 to about 1.8:1. In yet another aspect the invention relates to a method for producing improved, stable, aqueous suspension fertilizer compositions containing monoammonium phosphate as the phosphate source wherein the composition is formed by admixing the ingredients in an agitator equipped mixing vessel for a period of time effective to form a suspension. In still another aspect the invention relates to a method for producing improved, stable aqueous suspension fertilizer compositions containing monoammonium phosphate wherein the composition is formed by admixing the ingredients in an agitator-equipped mixing vessel wherein the rim speed of the agitator is at least 5,000 feet per minute.
Liquid mixed fertilizers have long been known in the art. In recent years, the use of multi-nutrient liquid mixed fertilizers has grown rapidly. However, such liquid mixed fertilizers have encountered serious drawbacks, when compared with the well established solid mixes or straight nitrogen liquid fertilizers. One major problem of liquid mixed fertilizers of the prior art has been the complex solubility characteristics of such fertilizer compositions. Because of complex solubility problems, crystallization (commonly called "salting out") has occurred during storage and transportation of liquid mixed fertilizers and these crystals have often clogged transfer or application equipment. In efforts to prevent such salting out, the compositions of the prior art have employed the use of polyphosphate compounds. In such formulations the polyphosphates are used as the sole source of phosphate or in combination with orthophosphates in the liquid mixed fertilizer compositions because of the desirability to obtain a higher solubility. When employing polyphosphates in the preparation of liquid mixed fertilizer compositions external heating and cooling of the reaction vessel have often been required to achieve favorable process conditions. Thus, the prior art methods of producing liquid mixed fertilizer compositions have often been limited in production rate because of temperature control requirements.
Because of the demand for additional crop production in the world market today, new fertilizer compositions and methods for producing same are constantly being sought. Especially desirable would be a mixed liquid fertilizer composition not requiring the conventional polyphosphate constituents and phosphoric acid. It is to an improved liquid mix fertilizer composition which does not require the use of phosphoric acid or polyphosphates that the present invention is directed.